


How to be a demon (and hide it)

by Raychu



Category: Ao no Exorcist | Blue Exorcist
Genre: Angst, Cross-Posted on FanFiction.Net, Demons, Exorcisms, Gen, Humor, Religious Imagery & Symbolism, demon features
Language: English
Status: In-Progress
Published: 2020-08-16
Updated: 2020-11-30
Packaged: 2021-03-06 05:35:06
Rating: General Audiences
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 5
Words: 5,555
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/25938259
Author URL: https://archiveofourown.org/users/Raychu/pseuds/Raychu
Summary: How do you hide being the son of Satan himself? How do you deal with a body that is unknown to you? How can a demon possibly become an exorcist without having his true identity discovered? Do tails have a life of their own? Are there classes you have to avoid? How far can you go without others getting suspicious? /Rin learning what not to do as a half-demon.
Comments: 20
Kudos: 127
Collections: Blue exorcist bests





	1. Fangs

**Fangs**

Keeping a low profile turned out to be harder than he thought it would be. Not only did his demonic side keep him from doing things that he used to do with ease, (like talking without accidentally biting his tongue) it also gave him inhuman strength. How could he possibly keep that a secret?  
  
Rin had always been stronger, he was able to carry more than an average teen his age, and in some cases, even more than a full-grown man, but this natural strength had doubled after his demonic powers had been returned to him. He was not only stronger, but his agility and his senses had also improved as well. What had not improved was his concentration. His patience had surprisingly grown weaker thanks to sensory overload, and his temper remained the same. Therefore, when he found out that his brother wanted him to read books meant for younger kids, he decided not to. He was not stupid, his level of intelligence was... Decent. He learned by doing and not by reading.

Like how he had tried to use his fangs on different objects to see how sharp they were. He had not been able to sleep much the first nights, the dorm feeling more like a prison than a home, so instead of looking at the ceiling until morning arrived, Rin decided to test his new features. His first victim had been a water bottle. He bit into the bottom of it and created a tiny hole, liquid soon pouring out in a stream. He made a couple more just for the heck of it, watching as it turned into a fountain. Another bottle fell victim when he tried to boil the water inside, only for it to somehow combust in a flare of blue flames. He had no idea as to how that even happened, water usually extinguished fire. Were blue satanic flames an exception? They quickly died out anyway, so no harm was done and no reason to panic. He knew he couldn't read about this stuff, it had to be tested.

Now was the time to move on to something more challenging. The next victim of his experiments: a basketball. He found this thing earlier that night as he roamed the building. It was fully inflated and bouncy, and he would have left the human habitat to play around with it, had he not been too anxious to do so. What would happen if someone saw him do something inhuman? Surely, no one would be outside at 3 AM, but was it worth the risk?

No, he did not know his own strengths or limits, it would be better to stay inside like a good little prisoner until he knew himself better. That did not mean that he would not attend classes, but he would have to be careful. When his mind finally settled down, he sat down and let his fangs penetrate the orange thing. It slowly deflated, leaving him with a flat, no longer bouncy ball.

This made his tail wiggle left and right in excitement. It didn't even hurt, so there had to be more solid things that he could leave a mark in.

There were still at least an hour until sunrise and the furniture in the room he had been practicing in now had bite marks in them, objects were left broken or punctured, and a few items somehow managed to flare up by accident. It looked like some kind of animal had caused havoc in there. 

Therefore, when his younger brother asked him whether he had been studying, he had been quick to blame the material given to him and say he had been reading manga. This way he avoided telling him what he really had been doing. He was lucky that the building was this big or Yukio might have discovered it. Still, it had not been a lie; he needed to try things out and not just bury himself in books. That was how Rin somehow talked his brother into taking him with him to observe an exorcism, and how he learned not to touch gates without permission. Also, biting into metals would cause serious toothaches.


	2. Symbols

**Symbols**

Of all the things he had to get used to, Rin Okumura had never thought that simple symbols and holy sentences would become an obstacle on his path to kill Satan. Even though he was not a full-fleshed demon child send to Assiah to destroy humanity, he would still feel the effects of a cross, a bible verse or a ritual. Some would affect him while others would do nothing worth mentioning.

"Blessed are those who mourn, for they will be comforted." He mourned, but he did not feel comforted. The holy words would comfort those who had sinned and regretted doing so, those who feel grief from wrongdoings, yet he did not feel any blessings send his way. Instead, he felt judged, those words were not for him, and he knew that. If there really were a god, then why would he bless a demon?

"And the devil, who deceived them, was cast into the lake of fire and brimstone where the beast and the false prophet are. And they will be tormented day and night forever and ever." Yet another verse. This one gave him goosebumps, a cold chill traveling down his spine, and ended at the tip of his tail. He found himself taking on his jacket to stay warm, all color draining from his face. Was he simply imagining things? Maybe he took the words personally, that had to be a good reason for him to feel this weird. He was not sure, all he knew was that this feeling was new, and he did not like it.

Yet he stayed put and listened, ignoring the side effects of each verse as they practiced one part after the other. He found his tongue to be burning when he had to read something aloud and lips starting to swell, as if he was having a battle with himself. So far, he was losing the fight.

"Therefore submit to god. Resist the devil and he will flee from you." The students raised a cross and repeated the sentence. Okay, he was not simply imagining things, his heart started to beat faster and it felt like small spiders had somehow managed to get under his skin and started crawling around, biting as they did so. He found himself scratching his arms and not daring to lift the cross just yet. This rewarded him with a glare from the teacher. Was he keeping an eye on him? Why?

Once most of those cursed verses were finally over, they moved on to symbols. Here he found himself going through all kinds of emotions and physical states. He went from freezing to suddenly sweating and feeling hungry. He then suddenly had the urge to tear his skin off and cry for no apparent reason.

However, he still stayed put. He would become an exorcist, even if that meant that he had to torture himself to do so. It was not as everything they did or said hurt him, it was manageable, and he needed to know his limits. What was the point of being there if he could not attend class? Rin had made it just fine without anyone getting suspicious, and when Shiemi asked him whether he was feeling okay, he had lied and said that he was just a little tired. It was not new to him to dose off in the middle of a lesson, so nothing strange there. However, to tell the truth, he was exhausted, and everything ached. She did not seem to believe him, yet she went back to write notes.

The teacher told the class to study the metal cross lying on their desk, the same one he had asked them to lift earlier. Finally feeling brave, Rin had reached for it, only to cry out and redraw his hand. His hand burned upon touching it and left a mark in his palm. He inwardly cursed himself for being stupid enough to try something like that in public. The class went quiet and turned their eyes to him. He hid his hand and gave them an awkward smile in return, blaming that the cross was cold to the touch and that he was feeling a bit under the weather, which would explain why he kept taking his jacket on and off.

He flinched when Shiemi suddenly placed a hand on his forehead, only to withdraw it as fast as Rin had upon touching the cross. "You are burning!" she exclaimed, and for a second he thought she meant that quite literally. "You are having a fever." She stated and he shrugged. He was not feeling his best, but that had nothing to do with an actual illness so it should not be a problem.

How wrong he had been to ignore it. After refusing to leave class, determined to stay put and continue as if nothing was wrong, he started to tremble, went through a short Epileptic-like seizure and fell unconscious upon hearing Bon recite another sacred verse. He sure as hell had gained everyone's attention by now, though Bon brushed it off as if it was nothing. "Oi, he fell asleep, so what? That whole act of his was probably just bullshit trying to scare us. That kid ain't normal."

The class went quiet once more. Only after Yukio entered to collect his fainted older brother and pretended to take him to the nurse, did the class start up again from where they left.

He ended up staying in bed for the rest of the day, a burning rash covering his neck, mouth and hands after being in contact with certain religious objects. This had been a lesson learned: If sacred verses and symbols make you feel like you are about to collapse, then find a reason to leave class for a couple of minutes instead of being a stubborn ass. He sure hoped those side effects would only be temporary, or he might have a serious problem finishing cram school.

**Notes for the Chapter:**

> A reminder that this was originally shared on FF.Net, but I decided to share it here as well, one chapter at a time.


	3. A passion for cooking

**Notes for the Chapter:**

> This one's a bit shorter. Happy reading!

Rin was not particularly talented. He never found an interest in art, the whole act of patience as you draw a line that somehow is supposed to connect to another line, to create something and then add details to it, that was not his alley. He was no good at playing instruments either. When his music teacher at school told him to sit down with a guitar and play a few chords, his patience ran thin and he ended up breaking the damn thing. They sent him home from school that day with yet another bill for his father to pay. Dancing didn't work out, and his singing was terrible, sounding like a cat being hung and slowly dying from lack of oxygen. He wasn't good at school either, at least not the sitting still and paying attention part. He didn't understand math, English classes made him fall asleep, and science was as complicated as the math classes. The teachers were all jerks, and as much as he liked to run around, he hated P.E. Whose idea was it to always play dodge ball? Surely, they could find something better to do than to throw balls at each other for an hour. In the end, Rin would always get a timeout for being too violent. If he couldn't go all out, then what was the point?

Cooking class was the only class that he had enjoyed before his father took him out of school. There he could be creative in a way that didn't keep him stuck in one place, and the food that he made would make others delighted and satisfied. The teacher adored him and always gave him kudos for every dish, even those he was less proud of, like the first time he made tempura udon and used too much spice. His adoptive father Shiro would eat whatever Rin brought home with him, both the good dishes and the bad dishes, and he would be proud of every single one of them.

Getting praise made Rin eager to try new recipes and experiment with all sorts of meat, vegetables, spices, noodles, sauces, to see what goes well together and what does not. The feeling of cutting into eatable things made his blood boil, a burning passion only growing for every meal well prepared and presented, drool running down his chin when steam arose from the pans and pots. When he was cooking, he could be himself and forget about the world around him. He wasn't a demon here, he was just a normal boy doing something that he loved to do. All troubles would melt away like butter on a frying pan, and the fear of losing himself to a greater good would stale for a short while, as he put his heart and soul into the masterpieces he made. He could make anything taste good, and that was his talent. He may not be good at music or math, but he could make one hell of a meal. Cooking was where he showed remarkable enthusiasm and devotion, and no one could take that away from him.


	4. Holy water

**Notes for the Chapter:**

> Sorry for the late chapter, been rather busy lately! I'm in the process of writing a book.

**"How do you make holy water? Burn the hell out of it!"**

* * *

Rin knew that he could not avoid it forever. One way or another he would get into contact with the sacred liquid, and it was going to hurt, a lot. He had hoped that it would not happen in front of his classmates. If it did, then that would be enough to reveal that he was the spawn of a demon, and it would cause fear and hatred towards him.

He had been lucky so far. He was running late on the day when they had a class about it, and that one time where someone spilled a whole gallon in the hallway, he just about stopped himself from stepping into the wet death trap. What would have happened if he stepped in it back then? The thought alone sent a shiver down his spine.

Bon was getting suspicious of his behavior; Rin could feel him watch over him with wary eyes ever since they had physical education class a week or so ago. Rin jumped in front of the reaper to save Bon's life. The Reaper did not attack him, and Rin did not have any injuries afterwards. That alone was enough of a reason to notice that the Okumura twin was different. He had noticed it himself as well; he ate in a different way now that he had fangs, his hearing had improved, and when he flared up, he saw the world in nothing but shades of blue. Then there was the fact that he could understand demons. The reaper stopped when he told it to. He was not sure why, but it was a possibility that it knew that Rin was the son of its master. What would happen if someone saw him try to have a proper conversation with a demon? They would figure him out eventually.

He just hoped that day would not be today.

They were having a drill, one that included low-level demons and holy water. That was all they had to do, spray holy water on the demons that now ran loose in the cram school. It was rather simple, however, instead of doing what he was supposed to do, Rin ended up running around, jumping back and forth in an attempt to avoid the liquid as well as the demons, all while trying not to gain attention. The old fart had warned him about it, and so had his brother, even Samael had advised him to stay away from it. If he was in danger, then why had no one told him to stay home from class this morning? Did they like to see him suffer a potential panic attack, or worse, burned off flesh? If that happened, then he would not only suffer, he would most likely be discovered.

He was carrying canisters of it, ready to throw, or at least pretend to do so as he ducked an attack from one of the larger demons. It was staring at him, and despite the situation, Rin still avoided throwing the water. He jumped over obstacles in an attempt to escape, even went as far as to do a short wall run. He could not draw his sword, he could not throw any verses at it as he risked hurting himself in the process, and he could obviously not throw the damn water grenades. Just what could he do then? Nothing came to mind other than dodging the attacks. Even for low-level demons, they were quite strong for someone who could not risk fighting back. He could send a few kicks and punches, but that was about it. What a great exorcist he was, but what did he expect?

Before he got a chance to get away from the beasts, one lashed out, sending Rin straight into one of the walls in the hall, leaving a small crack as he pushed himself off. It was not that bad, all it gave him was a slight headache and a sore back. No, this was nothing, he had been through worse. He found himself getting back up, only to realize that something was starting to soak his pants. At first he thought nothing of it, but by the time he realized that one of the canisters had sprung a leak, it was too late. The water made contact with the skin, and within seconds, it started to burn his flesh, making the young exorcist cry out in pain. This was what holy water felt like, complete and utter agony, the sensation of having your flesh burned off to then tear up the muscles, making it nearly impossible to even attempt to do anything but lie down and cry out in distress. He felt pathetic as he lay there on the ground, fumbling with his belt as he tried to unbuckle and take off his pants to make it stop, yet his hands were shaking too much and his vision was getting blurry. The fact that the floor was wet as well only made things worse, making him wail as smoke rose from his melting, squirming body. He was being tortured, and he could do nothing but to watch as his hands started to bleed, completely and utterly aghast with horror. He had only been laying there for a few seconds when shots were fired, boring through the demon who disappeared in a cloud of dark smoke.

Just as Rin thought that he would not make it out alive, a loud "Nii-san!" rang through the hall, followed by someone pulling him away from the puddle of water he was currently dying in. Within seconds he had been stripped naked, clothes thrown to all sides as his savior did all he could to get his older brother dry and out of danger. Once that was done, Yukio took off his jacket and covered Rin in it to keep the burned, bleeding flesh hidden from the others, as well as letting the fabric soak up the last drops of water still covering him, all while he still lay on the ground, crying. Within the short amount of time it took from getting into contact with holy water and till he was dry again, the liquid had done an immense amount of damage, making it impossible for the demon teen to move much. It was like having a severe sunburn, no, like dipping yourself in boiling oil. Yukio was trying his best to keep his brother conscious, but even the slightest contact with his skin made him cry out even louder. He wanted to throw off the jacket wrapped around him, but the other students were now running towards them. He was heaving his chest, desperate for oxygen, which only made him panic more. Before he could even begin to comprehend what was happening, everything went black and sounds started to faint away. He was unconscious.

Shiemi started to panic and wanted to take off the coat to look for fatal injuries. Knowing that Rin's injuries were demon-related, Yukio could not allow her to do that but instead used excuses like "he's naked underneath" and "it's okay" to dissuade her. Yukio insisted he would take him to the nurse's office and everyone else should continue their lesson. Only this time he meant what he said. This was too serious to treat at their dorm, and he had to fight off the panic that only seemed to grow as he picked up his older brother and started running towards the infirmary. It did not matter that Rin was a fast healer, every second counted when it had to do with holy water. Had he only known that they were having a drill that morning, yet he had been just as surprised as the rest of them, and before he could warn his twin, it had been too late.

Ryuji's suspicions only seemed to grow after that, and it would keep him awake at night. Just who is that kid? What was so special about him? Why was he getting special treatment? Why did he jump in front of the reaper? How did he even manage to pull off a jump like that? All these questions and yet none answered, he could not seem to put the pieces together. He was pissed. Why could he not figure him out? He had to find the answers to it all; he had to gain knowledge of his sharp-toothed teammate.

**Notes for the Chapter:**

> Reviews are appreciated!


	5. Haunted part 1

It was early afternoon; the sun was bright and there were barely any clouds in the sky. It was one of those days where all you wanted was to lie down in the grass right under a tree and take a long, pleasant nap.

Unfortunately, a field trip on that very day ruined those dreams and only a few weeks after the holy water incident. Rin had healed within a day, yet he could still feel the pain mentally. He had been lucky to survive. Had it been a greater amount of water, then who knows what would have happened. Probably nothing he couldn't survive, but the thought still made him feel ill and achy. Yet that seemed like nothing compared to what he went through the week after.

He and the rest of them had become exwires, yet that didn't change the fact that Neuhaus wanted him dead. He had tried to kill him on top of the old male dormitory, and he may have succeeded had Rin's healing abilities not been inhuman. Though holy water hit him, it did not have the same effect as it did the first time around. It seemed that the more he went through, the stronger his resilience became. That, or he had been lucky enough to get hit by thinned holy water.

Even after being stabbed, the instrument going all the way through his abdomen, he couldn't seem to die. He did not even fall to the ground, he stayed on his feet. It hurt, it had been pure agony, one different from the suffering he endured a week earlier, but still inexplicably painful. Yet he healed back up the moment Neuhaus pulled it out of his stomach.

He was truly a demon, there was no doubt about it, and yet at night, when the moon shone through the windows in their dorm, he denied it. He was no demon. How could he be? If anything, that was only a part of him. The other was as human as it could possibly be. Why could no one see that? Why did the demonic side of him have to rule out the fact that he was born by a human in Assiah? Would the same thing happen if his teammates found out? Would they try to kill him as well?

Despite feeling crestfallen, Rin still joined the trip, knowing that he needed the experience to become an exorcist. He couldn't give up after two almost fatal accidents.

It was a long bus drive, Shima and Shiemi had both fallen asleep, and while Rin was tempted to close his eyes as well, he found himself unable to do so. He was feeling a sudden paranoia, as if someone was glaring at him. At first, he thought he was imagining things. No one knew about his true identity, so why would anyone glare at him? Suddenly feeling insecure, Rin secretly looked around, moving his head as little as possible to avoid giving himself away. Upon looking to his right, he got eye contact with Bon, who quickly looked away. How long had Bon been staring at him? Why was he starring at him? He was sure that they had become mutuals by now, so why? Maybe he had some crumbs around his mouth. Now feeling self-conscious, he rubbed at his mouth with his sleeve.

Upon getting to their destination, Rin was the first one to leave the cramped bus. They soon stood in front of a tall, rather normal looking building. Yukio took a step forward, adjusted his glasses, and then turned around to face the group.

"Now listen up, this is important. The moment you enter this building, you cannot get back out through the door you entered. Find the other exit, which in this case will be the entrance, as you enter through the back door. Do not try to find your way out through logic. You may enter through the first floor, but the moment you are inside, you will find yourselves on the fourth floor. From there, find your way down. They say demons haunt this building. Some of those reported include ghosts, some being fetishes of both low and high levels. As you all know, fetishes can possess objects. Other than ghosts, some have seen low-level Goblins, most being in the basement. However, I would advise you not to enter the basement level; from there it will be harder to find your way out. Your primary goal is to find your way out. Many have gone missing since they entered, so be careful and avoid rooms that seem suspicious. You will exorcist as many ghosts as possible, but remember, it is not a priority."

As he finished his speech, he let the group walk past and towards the stairs, handing out a few things that might be of use. He did not fail to notice their nervous expressions. This wasn't notably safe, it was risky, but Yukio had faith in them. At least most of them. As his older brother was about to walk past him, he grabbed his arm and yanked him back.

"Rin, be careful in there. Do not pull your sword unless you are alone, and if you end up lost with no one else by your side, then do not get too close to the walls. The building itself might try to keep you from escaping. It knows what you are from your aura. Try not to go solo, stay within sight of others."

"Yeah, yeah, I got it. Teamwork. Though I gotta say, I think Suguro is acting strange. I don't think he trusts me at all... How am I supposed to help if I have to stay near them?"

"Figure that out yourself." With that, he let go of his brother, watching as he and the others entered the haunted building. There was no hoping they would all find a way back out before midnight.

The door locked itself once the students were inside, making them flinch from the sound. They were on their own now.

Sure enough, they were not on the first floor. Looking through a window proved that. Hitting it turned out ineffective.

"So, where are we going?" Shima was the one to break the silence as they walked down a dark hall, the only source of light being a single fluorescent light hanging above one of the many doors. No one had an answer to his question.

"I don't know, but we should stay together. If we split up, we may not find each other again." Rin stated, which rewarded him with a few glares.

"I can't believe you just said that. Ain't you the one always running off?" Bon replied in a sour tone. "You never tell us what you're up to. How is that teamwork?"

Rin wanted to answer but found himself at a loss for words. What could he possibly say that would not sound distrustful or disputable?

"Know what? Whatever. Just don't run away this time." Bon sighed and reached for a doorknob. Upon opening the door and looking inside, he found himself in the exact same hall, but a few meters behind the others instead of ahead. He hurried to pull himself back, then closed the door and turned to look at them. "Uh, not that door."

"Then what about this one?" Rin ran over to a brown old door and opened it, only to find an almost empty room, except for an old, dirty bed. "Not this one either."

Just as he was about to close the door, someone, or something, pulled him inside. Before he knew it, the door closed, and the last thing he heard was Shiemi crying out his name. When he reopened the door, he was in another hall, and no one was in sight. Great, he was already lost.

He entered the hall with a feeling of dread, hands shaking as he reached for his sword upon hearing a whisper not far from where he stood. His brother would kill him once he found out about this, unless Bon killed him first.

That was when the lights turned off, leaving him in complete darkness. Good thing he could see a bit in the dark, or he might have had to take out the flashlight Yukio handed him. So far, he did not need it. It was easier to keep a low profile if he kept himself in the darkness rather than lighting up the abandoned hall.

Why were they even there? These kinds of scenarios, weren't there professionals to deal with these? Not that he was scared or anything. It was cool and all, but he had no idea how to get out of there, no clue at all. What if the others escaped, but he didn't? Was he going to die there? No, if it was that dangerous, then Yukio would not have allowed them to enter. Still…

The sound of something roaming around in a nearby room pulled him out of his thoughts. Maybe he wasn't as lost as he first thought. Thinking that it might be the others hiding behind the door, Rin opened it, only to find it empty. Before he had time to close it, something rolled into his foot. It was a ball, a small, blue, soft ball. Thinking nothing of it, Rin reached for it, only to watch it roll off and down the hall at a slow pace. Could this be a fetish? Then again, he might simply be going mad. Whatever the case might have been, the half-demon followed it.

Just as he thought he had caught up to it, the ball started bouncing, and it sped up. The exwire now had to walk much faster to keep up with it. Just as he was at an arm's reach from it, it took off from the ground, now bouncing from one wall to the other, making it even harder to catch it. There was no longer any doubt, this thing was a fetish, and it was trying to get away. Rin winced when the ball demon knocked down a painting, the sound of it crashing to the ground sending a shiver down his spine. Why did he have to be alone? As much as he hated to admit it, he hated being alone in spooky places. As exciting as it could be, and despite his adventurous spirit, being surrounded by darkness and possessed objects gave him the creeps, and not in a good way.

Once again, he reached for his sword, but before he could draw it, he thought better of it. He had to do this without using Satan's powers. If he always relied on them to get him out of tricky situations, then he might as well give up on everything. But then again, no one was around to witness it, and he had no other way to exorcist the ghost other than using his flames. If there was a way, then he had no idea what that way might be.

Before he got a chance to choose, the ball disappeared through a door that closed and locked itself right after. It was by then he realized he was not in the hall anymore. He was in a room, one that looked like a small cafeteria, or a large dining room. Rin felt a presence, one that he could not quite identify, so when he felt someone standing behind him and a hand touching his shoulder, he found himself unable to move.


End file.
